Biographical Data :

Al-Zarqali carried out a series of astronomical observations at Toledo and compiled them in what is known as his famous Toledan Tables, which were translated into Latin in the 12th century.

Al-Zarqali corrected Ptolemy’s estimate of the length of the Mediterranean Sea from 62 degrees to approximately correct value of 42 degrees. He was first to prove conclusively the motion of the Aphelion relative to the stars. He measured its rate of motion as 12.04 seconds per year, which is remarkably close to the modern calculation of 11.8 seconds.

Al-Zarqali invented the apparatus, a flat astrolabe known as Safihah (Azafeq), which was widely used by navigators until 16th century. Its details were published in Latin, Hebrew and several European languages.

Al-Zarqali known in the West, as Arzachel was born Abu Ishaq Ibrahim Ibn Yahya al-Zarqali in Spain.